1. Field of the Invention
The present invention relates to a three-dimensional (3D) image display device, and in particular relates to a naked-eye type 3D image display device, and an image display device, and electrically switchable light modulating cells thereof.
2. Description of the Related Art
In Nature 425, 383 (2003), Hayes et al. discloses a novel on/off switch method, which applies an electrowetting principle to control colored oils. This technology has several advantages such as high color saturation, high image response speed, and low energy consumption, as compared to conventional technologies. Therefore, electrowetting was soon applied in the display technology field thereafter.
In U.S. Patent Publication No. 2009/0257111, a tunable optical array device includes a substrate on which a TFT tuning circuitry is disposed thereon for controlling an upper layered cell array, as shown in FIG. 1. Two incompatible fluids having different polarities are filled in cells of the cell array, and the shape of the interface between the fluids is controlled by lower layered TFT tuning circuitry. Accordingly, phase modulation and beam deflection of light beams traveling through the cell array may be controlled. Also disclosed are driving methods of the TFT tuning circuitry. However, using a TFT driving mechanism may dramatically reduce the aperture ratio of the display. While an interconnect layer is also disclosed, the brightness of the display is reduced by the multi-layered structure of the interconnect layer. An electrowetting display having multiple cells is applied in a holographic reconstruction system. Interference fringes of light beams are generated through the electrowetting cells. The electrowetting display may deflect the light beams traveling therethrough to the eyes of a viewer. Although the electrowetting display may deflect light beams, it lacks the concept of time-multiplexing. The electrowetting device may be applied in retro-reflective panels, image projection devices, and holographic projection reconstructing equipments.
U.S. Pat. No. 7,474,470, titled “Devices and methods for redirecting light”, discloses a light redirecting device including a display element and a plurality of redirecting elements thereon, as shown in FIG. 2. There is no special structure or hydrophilic layer on interior surfaces 106a-c of the redirecting element, such that liquids L1 and L2 may be misplaced. The liquids L1 and L2 are incompatible, and interface shape between the liquids may be controlled by a top electrode 110. By switching the electrode, the liquid interface forms several shapes to redirect light for display 3D images. In addition, the light direction may not be exactly controlled due to the fact that the contact angle of the liquids may mistake while a voltage is applied to the light redirecting element.
U.S. Pat. No. 7,817,343, titled “Electrowetting lens”, discloses an electrowetting lens, which includes two fluids of different polarities. The liquid surface may be controlled by applying same voltages to first and second electrodes, respectively. For saving the energy, only the electrodes near the liquid surface (not all electrodes) are driven by the voltage. However, this design needs a specific circuit layout to individually control each electrode, and it may increase design complexity.
In related arts, liquid lenses made of mini-scaled capillary array devices have been manufactured by micro-electro-mechanical system (MEMS) processes. The capillary surface may be an interface between a gas and a liquid or between two liquids, and the shape of the interface is determined by surface tension of the liquids. In Applied Physics Letters 87, pp. 134102 (2005), Hirsa et al. published a paper titled “Electrochemically Activated Adaptive Liquid Lens”, a reversible capillary switch having low energy consumption is formed on a single chip.
U.S. Publication No. 2009/0316003, titled “Pinned-contact oscillating liquid lens and image system”, discloses an oscillating liquid lens, which utilizes the capillary force between the liquid droplet and the channel of the liquid lens to support the liquid droplet. The liquid lens is driven by changing the chamber pressure, thereby deforming a first part of the liquid droplet and a second part of the liquid droplet. As such, an incident light traveling through the chamber may be focused or diffused.
Displays capable of showing stereoscopic images or animation are called three-dimensional (3D) image displays. Major developments in the 3D display fields have led to two types of technologies: a polarized glasses type and a naked-eye type. Meanwhile, 3D display effects may also be theoretically accomplished by using holography. However, holography needs small pixels and huge memory/calculation speeds. The naked-eye type is an easier 3D display method due to the fact that only a beam control element is located, such as a barrier layer or a lenticular lens, directly before the display. As such, the deflect direction of the light beam may be changed or controlled by the naked-eye type, such that right eye images and left eye images may be deflected into the right eye and the left eye of a viewer, respectively.
In U.S. Pat. No. 6,369,954, titled “Lens with variable focus”, a lens having an adjustable focal length is disclosed. The lens includes a chamber filled by a first fluid and a second fluid, wherein the droplet-shaped second fluid contacts the chamber surface. The first and second fluids are transparent fluids of different refractive indexes, and they are incompatible to each other. An electrode is plated on the chamber surface to contact and surround the chamber surface. Because the first and second fluids have different fluid properties, the interface curvature ratio between the first and second fluids may be changed by applying an external voltage. The focal length of the incident light may be adjusted by changing the interface curvature ratio between the first and second fluids.
U.S. Pat. No. 7,688,509, titled “AUTOSTEREOSCOPIC DISPLAY”, discloses liquid lenses, collocated with splitting screens, to display 3D images. The electrodes in an electrowetting cell include side electrodes and a bottom electrode. The electrowetting lens is operable by applying different voltages to the side electrodes and the bottom electrode, such that a curvature ratio or a tilt ratio of the interference of the two incompatible fluids is tuned to modulate the emission direction of light beams traveling therethrough.
According to related arts, the light modulating element manufactured of the electrowetting concept has problems as below. The polar and non-polar solvents injected in the light modulating element have similar densities. When the adhesive force between the liquids and the surface of the light modulating element is insufficient, the first and second liquids may be misplaced. Furthermore, the first fluid surface is easily deformed when applied with a voltage, and the first and second fluids are easily misplaced due to insufficient adhesive forces between the liquids and the surface of the light modulating element. Even if the applied voltage is stopped, the tension between the polar liquid and surrounding object is too small to make the polar fluid return back its original shape/position.